A sampling system in breath alcohol-measuring devices delivers a small quantity of gas of an accurately defined volume (0.3 mL to 1 mL) from the breathing air flow into the alcohol sensor.
These systems usually comprise a piston, which is driven by a small electric motor, as described in DE 3904 994 A1, or of a bellows, which is compressed by a pushing magnet, as disclosed in DE 203 10 500 U1.
Both systems have specific drawbacks. An electric motor with a gear mechanism and a piston has limited reliability and has a low speed of response (<0.5 sec) because of the inertia of masses. A pushing magnet is relatively large and energy-intensive relative to the stroke. Also, only switching between two fixed end positions is possible with a pushing magnet. Therefore, such a pump can also only deliver a fixed volume, so that two pushing magnets are needed for the function described in DE 203 10 500 U1.